To address the inherent trade-offs between the size, resolution, and field of view (FOV) of thin clinical endoscopes, we propose a novel ptychographic endoscope based on the Fourier ptychography (FP) technology. Ptychographic endoscope uses angularly varying illumination to extend the performance beyond the limit defined by the optical system. It has the following key features: (1) the achievable resolution of ptychographic endoscopy system is determined by the largest incident angle, not the numerical aperture (NA) of the employed miniaturized optics; (2) it is possible to recover the high resolution sample image and correct for remaining aberrations of the employed optics, enabling a much larger design space; (3) the recovered high-resolution images at different depths can be used to construct a 3D image of the tissue topographic structure; and (4) with continuous illumination, the instrument works as a conventional low resolution endoscope. When high resolution imaging is needed, it works in FP mode with sequential pulse illuminations. The goal of this proposal is to develop thin endoscope and image reconstruction algorithms to demonstrate the ptychographic endoscopy system, by pursuing the following aims: (1) develop the ptychographic endoscopy system using miniaturized optics and illumination fibers (Month 1-14); (2) develop a high speed image construction platform to construct a high-resolution image over large FOV and large depth of field in real time (Month 1-15); and (3) characterize and evaluate the imaging performance of the ptychographic endoscopy system (Month 14-24). Ptychographic endoscope is compact and doesn't require a complicated system, it is also low cost because only a ring illumination source is needed. Most important, it addresses inherent trade-offs between the size, resolution, and FOV of thin endoscopes. Successful completion of the proposed ptychographic endoscope will enable us to develop thin endoscopes for unmet clinical needs by enabling clinicians to accurately detect and diagnosis diseases, particularly in regions with limited access.